Game of Life example: Remove enumerated type

Due to #58, enumerated types currently don’t work in the web runner. Since it seems unlikely that this issue will be resolved soon, this commit removes the enumerated type specification from the State class. This is kinda ugly, but still better than keeping an uncompilable example on the website, especially as it’s not clear at all why the code doesn’t compile (`alive`, `resurrected`, `moribund` and `dead` look like top-level objects, and most people don’t know that the whole code is wrapped into a single top-level function for running).